1. Field
Disclosed embodiments relate to an exhaust system for a battery in a vehicle, and more particularly, to an exhaust system for a battery in a vehicle such as an electric car (vehicle) (battery car) or a hybrid car (vehicle) including a motor that drives driving wheels, and two batteries, including a high voltage battery that supplies electric power to the motor and a low voltage battery that supplies electric power to a control system and auxiliaries.
2. Related Art
Vehicles such as hybrid vehicles or electric vehicles include a motor that drives wheels and two batteries with different voltages including a high voltage battery that supplies electric power to the motor and a low voltage battery that drives electrical components and auxiliaries.
The high voltage battery is generally housed in a casing (hereinafter referred to as a battery case) made of metal or the like in terms of protection from an impact, or invasion or entry of foreign matters and preventing a driver from touching a high voltage component. The high voltage battery may be heated by charge and discharge, which may result in reduction in performance or life. Thus, there are proposed a unit for introducing air in a vehicle interior such as cabin into a battery case by using a cooling fan to cool a battery when a battery temperature increases as disclosed, for example, in Japanese Patent Laid-Open Publication No. 11-195437 (Patent Document 1), and a method of introducing a cold air of an air conditioner for adjusting a temperature in a cabin directly into a battery case by using a duct to cool a battery as disclosed, for example, in Japanese Patent Laid-Open Publication No. 7-73906 (Patent Document 2).
On the other hand, the high voltage battery may emit a harmful gas (a hydrogen gas for a nickel hydrogen battery, a carbon monoxide gas for a lithium ion battery, or the like) when an abnormality occurs such as an internal short-circuit of a battery cell due to a collision of a vehicle, or overcharge thereof. In order to prevent the harmful gas from entering the interior of the vehicle cabin, the cooling fan may often functions as a blower that exhausts gas in a space around the battery from the vehicle (as disclosed, for example, in Japanese Patent Laid-Open Publication No. 2004-312920).
However, continuously driving the fan in a state where cooling of the battery or exhaust therearound is not required increases power consumption and reduces life of the fan, thus, undesirably reducing a vehicle travelable distance by using only electric power stored in the battery particularly for a plug-in hybrid car or an electric car. Therefore, a technology is desired of driving a fan in a minimally necessary manner, and exhausting a gas reliably and quickly in an occasion of detecting generation of a harmful gas is detected.
In order to deal with circumstances mentioned above, various technologies or means have been proposed such as:
a method in which a battery abnormality monitoring unit for detecting a battery abnormality state that may generate a gas is provided, and an exhaust fan is driven only when the battery abnormality monitoring unit detects an abnormality in a battery as disclosed in, for example, Japanese Patent No. 3864538 (Patent Document 3);
a method in which a ventilation fan is driven to vent air externally from an interior of a vehicle cabin when a voltage of one cell that constitutes a battery reaches a hydrogen gas generation voltage or more as disclosed in, for example, Japanese Patent Laid-Open Publication No. 6-217412 (Patent Document 4);
a layout of a battery exhaust structure and an exhaust pipe that allows a gas to be properly discharged from a vehicle cabin even in a collision of the vehicle as disclosed in, for example, Japanese Patent Laid-Open Publication No. 2007-320426 (Patent Document 5); and
a method, in which when gas generation is detected, an air introduction valve is opened and then a ventilation fan is driven to increase gas exhaust efficiency as disclosed in, for example, Japanese Patent Laid-Open Publication No. 2004-312920 (Patent Document 6).
However, the technologies (1) to (4) (i.e., disclosed in the Patent Documents 3 to 6) provide the following defects or inconveniences.
First, in the technology (1) (Patent Document 3) and the technology (2) (Patent Document 4), an abnormality in the battery is judged based on a value measured by a voltage sensor or a temperature sensor, and thus, the exhaust fan is driven only after the battery falls into a dangerous state. Therefore, these technologies are not optimum methods particularly at a time of collision of a vehicle at which possibly quick gas exhaust is required.
The technology (3) (Patent Document 5) aims to ensure a gas exhaust path even in a collision of a vehicle, which is not applicable to solve the above-described defect.
The technology (4) (Patent Document 6) assumes exhaust of a hydrogen gas in a nickel hydrogen battery to improve increasing gas exhaust efficiency rather than preventing a gas from entering a vehicle cabin. However, the technology (4) is not an optimum method because it allows a certain amount of gas to enter the cabin when a CO gas highly toxic to human body is generated in a lithium ion battery.
Further, in a collision of a vehicle, it is highly likely that an abnormality such as disconnection occurs in a power supply system such as an exhaust fan or an air introduction valve and a drive circuit. However, the technologies (1), (2) and (4) do not pay attention for operating a device for exhausting a gas against such occasions.
Furthermore, since any consideration is not specifically paid to conditions for stopping the exhaust fan, even in an dangerous case of gas generation, for example, it is likely that an exhaust function stops when a driver turns off an ignition switch, or that the exhaust fan is not continuously driven when a gas is generated during external charging, and when the driver gets into a vehicle, the driver inhales the gas.
In view of the above technologies, there is still room for improvement.